The invention generally relates to the fabrication of glass ceramic substrates for the packaging of semiconductor device chips and, more particularly, to the toughening of the brittle glass-ceramic substrates in a manner compatible with existing substrate processing cycles including high temperature sintering in the presence of oxygenating ambients.
As is well understood, the toughness of a ceramic is a material property which is a measure of the resistance against crack propagation when the ceramic is stressed. Glass ceramics, particularly based on cordierite, are not as tough as other structural ceramics such as alumina, silicon nitride, silicon carbide, zirconia, etc. It is desirable to enhance glass-ceramic toughness for certain applications and techniques have been proposed to achieve that end. It is known, for example, that fibers of metallic glass ribbon reinforcement of glass ceramic matrix provide improvement in the fracture toughness of the glass-ceramic matrices formed by heat treatment of the composites. This is described in papers by R. U. Vaidya and K. N. Subramanian, "Reinforced Glass-Ceramic Matrix Composites", Journal of Materials Science, 25 (1990), pp. 3291-3296 and "Elevated Temperature Mechanical Properties of Continuous Metallic Glass Ribbon-Reinforced Glass-Ceramic Matrix Composites", Journal of Materials Science, 26 (1991) pp. 1391-1394. The described toughening techniques reportedly include laying out the metallic glass ribbons within glass powders in a steel die, pressing the composite specimens at 3000 p.s.i., heating to 200.degree. C. to drive out organic binder and then sintering and devitrifying at 400.degree. C. and 450.degree. C., respectively. The problem of the toughening of glass ceramic substrates subjected to more rigorous high temperature (up to 1000.degree. C.) sintering in steam was not addressed.
Brownlow, et al., U.S. Pat. No. 4,474,731, discloses the steam sintering of ceramic materials containing conductive pathways suitable for the packaging of semiconductor device chips. This patent teaches a steam sintering cycle for glass-ceramic in which nickel or palladium is added to the glass-ceramic green sheets as catalysts for carbon removal by oxidation. NiO and Pd (NO.sub.3).sub.2 were used as the catalytic agents. Material properties of the sintered ceramic, such as toughness and strength are not discussed.